Signal for telephone trunk-lines.



No. 659,789. Patented Oct. [6, I900. H. M. CRANE.

SIGNAL FOB TELEPHONE TRUNK LINES.

(Application filed. 3511.10, 1900.)

(No Nodal.)

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llharrnn Srnrns EFFICEQ HENRY MIDDLEBROOK CRANE, OF NEYV YORK, N. Y., ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

SIGNAL FOR TELEPHONE TRUNK-LINES.

SPECIFICATION forming part of Letters Patent No. 659,789, dated October 16, 1900. Application filed January 10, 1900. $erial No. 920. (No model.)

1'0 (LU 107L077 it may concern.

Be it known that'I, HENRY MIDDLEBROOK CRANE, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented a certain new and useful Improvement in Signals for Telephone Tru nk-Lines, (Case No.1,) of which the following is a full, clear, concise, and exact description.

My invention relates to signals fortelephone trunk-lines, and has for its object to provide means whereby the receiving operator or B operator, as she is called, may be kept informed as to the condition of the trunk-line at the switch of the answering operator or A operator.

Heretofore it has been usual to provide a clearing-out signal at the board of the receiving operator to notify the receiving operator when the connection has been taken down'at the answering-board, so that she may remove the trunk-line plug from its connection. On most of the trunk-circuits ordinarily in use the clearing-outsignalis displayed at alltimes when the terminal plug at the receiving end of the trunk-line is out of its seat in the switchboard orinserted in a spring-jack,while no plug is in a jack of the trunk-line at the outgoing terminal, so that the clearing-out signal is displayed when a trunk connection is ordered over an order-wire fromthe moment the B operator connects the trunk-line with the called-snbscribefis line until the A operator makes connection from the callingsubscribers line to the trunk-line and again from the time the latter con nection is rem oved until the former is removed, the last-stated period being the proper time for the display of the clearing-out signal.

By my invention the display of the clearing-out signal during the first'described period is prevented, so that the display of the signal is never ambiguous, but always means one thing-i. e., a notice for disconnection. For this purpose 1 provide shunts for the clearing-out signal, the signal being shunted when connection is made from the trunk-line to the called line at the receiving-switchboard and being again shunted when connection is made with the trunk-line at the answeringswitchboard, the removal of the latter connection, however, causing the shunts of the signal to be removed, whereby its display is eifected. I further provide a guard-lamp at the receiving end of the trun k-line, which remains lighted from the time the trunk-plug is connected with the called-subscribers line until the A operator has connected the calling-line with the trunk-line by inserting her connecting-plug into the trunk-line springjack. While thisguard-lampremainslighted, it therefore indicates to the B operator that the connected trunk-line has not yetbeen made use of, thus obviating the possibility that an A operator could order a trunk-line connected with a called subscriber and then fail to make the connection at her end,leaving the called subscriber helplessly connected with the trunk-line to the A oflice.

My invention will be particularly described by reference to the accompanying drawing, which is a diagram illustrating, with the aid of conventional symbols, atrunk-line extending from an answering-board to a receivingboard, the said trunk-line being equipped with signaling apparatus and circuits of my invention.

The trunk-line is composed of two limbs 1 2, terminating at the answering-switchboard in the line-springs a a respectively, of the trunk-line spring-jack a and terminating at the receivingswitchboard in the sleeve-com tact b and tip-contact respectively, of the trunk-line plug 1).

As is a matter of common knowledge among telephone engineers it is usual for the receiving operator to make connections with the trunk-line plugs at the order of the answering operator received over a separate order wire telephone circuit. The ordinary circuits and the operation of such a trunk-line are well known in the art, and I have therefore shown in the drawing only the apparatus directly involved in my invention, so that the drawing will not be uselessly obscured. While I have spoken of the trunk-line as a continuous line and have applied the numerals 1 2 to the conductors which constitute the same, it is shown as divided into two parts at the receiving-switchboard B by a repeating-coil B, one side of which repeating-coil that is, the portions 0 c -being included in that part of the trunk-line which extends to the spring-jack at the answering-board and the other portions d d of the repeating-coil being included in that part of the trunk-line which extends to the plug b. A battery 6 is connected between the windings d d of the repeating-coil, and a condenserfis included between the windings c thereof. The third contact or shank b of the plug, which engages with the grounded test-ring g of the spring-jack of the called-subscribers line, is connected by a conductor 3 through the Winding of the relay h with the battery 6, whereby the relay his energized as soon as the plug is inserted in any spring-jack. The conductor 3 is divided into three paths between the battery 6 and the winding of relay it, one of said paths 4 including the clearing-out signal, while the other two paths 5 6 are shunts for the clearing-out lamp. Thus the path 5 leads from battery by way of the armaturelever and back contact k of a relay is and includes the resistance-coil [,which may be of, say, forty ohms resistance. The other path 6 leads from the front contact of the arma ture-lever k to the battery, and the continuity of this path is further controlled by a relay n, the armature n of which, with its front contact 91?, forms a part of this conductor. The relay h has two armature-levers with their associated switch-contacts, one of which armature-levers controls the continuity of the tip-strand 2 of the plug-circuit, while the other armature-lever h is connected to ground through resistance m of, say, one hundred and twenty ohms. The front contact h for the armature-lever h is connected with the battery 6 by three paths, one of-which, the conductor 7, includes the guard-lamp 1), while the other two paths 8 5 and 8 6 include the winding of relay 7{; and the armature 70 lihQIeOfm Thus the two paths 8 5 and 8 6 constitute shunts for the guardlamp 19, one of said shunts 8 5 being by way of the front contact of the armaturelever 10 and including the winding of this relay. The other path 8 6 includes the winding of the relay and the armature Z0 and back contact 70 thereof and is also controlled by the relay n. It will be evident then that when the relay his energized current will flow through the conductor 7, including the guard-lamp 10, until relay n is energized and that when the relay n is energized the closing of conductor 6 by the armature n of such relay will complete the circuit 8 6, which includes the Winding of the relay is. Thereupon the armature 10 being attracted an independent shunt-circuit 8 5 will be established by way of the'front contact of armature 71: including the winding of the relay is, so that the guard-lamp will thus be permanently shunted independently of relay 9?. and controlled only by the armature h of relay h. The energization of the relay n will permanently shunt the guard-lamp, and at the same time the armature k of the relay It will break the shunt 5 about the clearing-out signal 2', substituting for this shunt another one by way of the front contact of the armature-lever 7t over conductor 6, and since the armature It will now remain attracted independently of the relay n it will be apparent that the clearing-out signal is now shunted only by way of conductor 6 and that this shunt will be opened when the relay n is denergized. The relay n then is the factor which at different times determines the display of both the guard-signal and the clearing-out signal, and to provide means whereby the re-' lay n may be controlled from the answeringswitchboard, the winding of the relay is included in a conductor 9, which extends from the battery-wire 3 to the limb 2 of the trunkline extending to the answering-board. An ordinary pair of plugs and their cord-circuit are shown at the answering-board A, and a repeating-coil is included in the usual manner-in the strands of this cord-circuit, together with the talking-battery, the side of the battery which is connected with the tip-strand being grounded at 0. It will be apparent, therefore, that the insertion of the operators connecting-plug in the trunk-line spring-jack at the board A will complete the circuit from battery 6, which includes the relay n, by way of conductor 9, winding 0 of the repeatingcoil R, limb 2 of the telephone-line, a shorter line-spring a of the trunk-line jack at the answering-board to the tip of the plug, and thence to ground at 0.

In order that the usual supervisory apparatus in the operators cord-circuit at the board A may be responsive to changes in the condition of the called line, means are provided for grounding the side 1 of the trunkline when the called subscriber responds. This is accomplished through the agency of a supervisory relay r, included in the side 1 of the trunk-line between the plug 1) and the battery 6. This relay is operated in the usual manner of supervisory relays-that is to say, it remains inert until the called subscriber responds; but when he does a path is provided from one side of battery 6 through a winding of the repeating-coil, out over the line to the subscribers station, through his telephone apparatus, and back over the other side of the line to the other pole of the battery. The armature of the relayr is connected with the side 1 of that portion of the trunk-line which extends to battery A between the winding 0 of the repeating-coil and the condenserf, and the front contact of the relay is grounded. It will be understood, therefore, that when the called subscriber responds current'from the batteryincluded between the cord-strands of the plug-circuit at the A board will flow from ground 0 through the supervisory relay, which is included in the sleeve-strand of the connecting-plug, to the sleeve of the plug, the long spring ct of the trunk-jack a, limb 1 of the trunk-line, winding 0 of the repeatingcoil, and armature and front contact of the relay 1' to ground. The relayr thus controls this circuit through the supervisory relay of the plug-circuit at board A, rendering that supervisory relay responsive to the flow of current in the called line, to which the trunkline may be connected at board B.

The operation of the apparatus and circuits above described is as follows: Upon receiving an order from the A operator to connect the trunk-line with the line of a called subscriber the B operator inserts the plug 5 into the spring-jack of the called-subscribers line. Making this connection completes the circuit of the battery e from ground through the winding of relay 7L by way of the shank b of the plug and to the grounded test-ring g of the called subscriber, current passing through the branch 5 of the conductor 3 by way of the back contact k and armature-lever 7c and through the resistance Z. The clearing-out signal-lamp t' being thus shunted remains dark. The current passing through the Winding of relay h energizes the core of the relay and causes the armature-levers to be attracted, one of said armatures completing the continuity of the limb 2 of the cord-circuit and the other armature h completing a circuit from battery 6 through the conductor 7, which includes the guard-lamp p, to ground. The guard-lampis thus lighted and remains lighted until a connectionis made with the springjack at of the trunk-line at the answeringboard. lVhen such connect-ion is made, the relay n will be energized by current from the grounded battery 6 through the winding of the relay to the limb 2 of the trunk-line by Way of the conductor 9, thence to the linespring a of the trunk-line jack, through the tip of the connecting-plug, and to ground at o. The energization of this relayn thus completes the circuit of conductor 8 through the armature-lever n and front contact n of the relay, so that the guard-lamp p is shunted by conductor 8, which includes the winding of the relay 712. This relay, it should be stated, is of comparativelydow resistance-say forty ohmsso that most of the current passing through the conductor 6 will take the path 8 through the relay in preference to the path 7 through the guard-lamp p, in consequence of which the guard-lamp Will be darkened. As soon as circuit is completed through the relay 7t by way of the path 8 6, however, the armatures 7t" 71: Will be attracted, the latter of which will close the independent circuit 8 5 through the winding of the relay by Way of conductor 5, the guard-lamp 19 being thus permanently shunted over conductor 5 by the low-resistance winding of the relay. The attraction of the armature k, moreover, changes the shunt about the clearing-out signal-lamp 2', so that instead of being shunted by conductor 5 by way of the back contact of the armature it it will now be shunted by conductor 6 and the front contact of said armature, the continuity of this shunt being controlled by the armature n of the relay n.

This conditionthat is, with the guard-lamp p and clearing-out signal-lampz' both darkwill continue to exist until the connection is removed at the answering-switchboardthat is, until the circuit through the relayn is broken by the removal of the ground 0 from the limb 2 at the answering-board. Then this connection is removed, the consequent denergization of relay n breaks the shunt S of the lamp t', which thereupon becomes lighted, indicating to the B operator that the trunk'line is no longer in use at board A and notifying her to remove the trunk-plug I) from its connection. Thus the clearing-out signal-lamp is dark while the B terminal of the lamp is connected, the A terminal not being connected, because of the inert condition of relay is, and is still dark after connection at the A terminal, because both of the relays 7t and n are excited, but becomes lighted while the trunk-line is still connected at the A terminal, because of the excited condition of relay is and the inert condition of relay n.

Having thus described my invention, what Iclaim as new, and desire to secure by Letters Patent, is

1. The combination with a telephone trunkline extending from a spring-jack at an answering-board to a terminal plug at a receiving-board, of a clearing-out signal '5 and a circuit 3 including the same with a source of current, said circuit being closed in registering contacts of the terminal plug and the spring-jack of the called-subscribers line, two relays 7t n controlling said clearing-out signal, a circuit through relay 7c controlled by the relay n and forming a shunt for the clearing-out signal, a circuit 5 adapted to be closed by the relay 7r when the same is energized, said circuit 5 including the winding of relay 7- to establish an independent circuit through said relay, the circuit 5 being in shunt with the clearing-out signal, and a circuit for the relay n completed by connection with the trunk-line spring-jack at the answering-board, whereby the clearing-out signal is continuously shunted While the ter minal plug of the trunk-line is connected, the shunt about said clearing-out signal being removed and the signal displayed when the connection with the trunk-line is removed at the answering-board, substantially as set forth. I

2. In a system of trunk-circuits between two switchboards of a telephone-exchange, a guard lamp or signal 1) and a clearing-out lamp or signal 1' combined with circuits With which said signals are connected, electrical apparatus, said apparatus including shunt ing apparatus or circuit-controllers, and a source of current brought into action by the plug and switch connections of the trunk-wine, whereby on making connection with the called line the guard-signal is displayed, said display of the guard-signal being caused to cease on inserting the connecting-plug in the trunk-line switch at the answering-board by a shunt-circuit controlled through the agency of said plug, the clearing-out signal being at this time also shunted, said shunt being adapted to be removed from about the clearing-out signal to display the clearing-out signal by the removal of the said plug from its switch at the said answering-switchboard, substantially as described;

3. The combination with a telephone trunkline extending from an answering-board to a receiving-board, of a signaling system for the trunk-line comprising a clearing-out signal 0) and a guard -signal p, and circuits and a source of current associated therewith for operating said signals, means for efiecting the display of the guard-signal when connection is made at the receiving-board from the trunk-line to the called-subscribers line, a relay n and switching mechanism operated thereby for effecting the concealment of the guard-signal, means, controlled by said relay, for bringing the clearing-out signal into action, the said clearing-out signal being controlled by said relay, and a circuit 9 for controlling said relay, said circuit 9 being controlled by connection with the trunk-line at the answering-board, whereby the guardsignal is displayed when connection is made between the trunk-line and the called-subscribers line at the receiving-board and is concealed when connection is made with the line at the answering-board, and whereby the clearing-out signal-circuit is brought into action when connection is made with the trunkline at the answeriug-board,-the clearing-out signal being displayed when such connection is removed, substantially as set forth.

4:. The combination with a telephone trunkline extending from an answering-board to a receiving-board, of a guard-signal p and a clearing-out signal z' at the receivingboard, a source of current e, a circuit 3, 4 including the clearing out signal and a circuit 7 in cluding the guard-signal, said circuits being closed when connection is made from the trunk-line to the called-subscribers line at the receiving-board, shunt-circuits about said signals, relay mechanism controlling said shunt-circuits, and a circuit 9 controlling said relay mechanism, said circuit 9 being closed by connection with the trunk-line at the an swering-board, whereby the guard-signal and clearing-out signal are shunted when the lastmentioned connection is made, and whereby the shunt about theclearing-out signal is removed when such connection is taken down, substantially as set forth.

5. The combination with a telephone trunkline extending between an answering-board A and a receiving-board B, of a clearing-out signal t' at the board B for indicating the condition of the trunk-line at the answeringboard, a circuit 3 including the signal with a source of current, said circuit being closed by connection from the trunk-line to the calledsubscribers line at board B, a relay 7c and a circuit including the same with a source of current, said last-mentioned circuit being adapted to be completed by connection with the trunk-line at the board A, two shunt-circuits for the clearing-out signal controlled by said relay, one of said shunts 5 being closed by the relay when the same is inert, and the other of said shunts 6 being closed by the relay when it is excited, a circuit, including the winding of the relay, closed when the relay is excited, whereby said relay is rendered independent of the apparatus at board A, and means controlled by the removal of the connection with the trunk-line at board A, for opening the shunt 6, substantially as set forth.

6. The combination with a telephone trunkline, of a clearing-out signal therefor at the receiving-terminal of the line and a circuit including the signal, a relay is and means controlled by connection with the trunk-line at both terminals thereof for exciting said relay, two shunts 5 6 for the clearing-out signal, one of said shunts 5 being normally closed by the relay, and a relay n controlled by connection with the trunk-line at the distant terminal thereof, the shunt 6 about the clearing-out signal being controlled at switch-contacts of both relays and being closed at the contacts of relay it when the same is excited, whereby the clearing-out signal is continuously shunted until connection with the trunk-line has been made and removed at the distant terminal, the signal being displayed on the removal of such connection, substantially as described.

7. The combination with a telephone trunkline, of a clearing-out signal therefor at the receiving-terminal of the line and a circuit including the signal, a relay is and means controlled by connection with the trunk-line at both terminals thereof, for exciting said relay, two shunts 5, 6 for the clearing-out signal, one of said shunts 5 being normally closed by the relay, a relay to controlled by connection with the trunk-line at the distant terminal thereof, the shunt 6 about the clearing-out signal being controlled at switch-contacts of both relays and being closed at the contacts of relay it when the same is excited, whereby the clearing-out signal is continuously shunted until connection with the tru nk-line has been made and removed at the distant terminal, the clearing-out signal being displayed on the removal of such connection, and a guard-signal 1) controlled by connection with the trunk-line at both terminals thereof, said guard-signal being displayed when connection is made with the trunk-line at the same switchboard and being shunted by a circuit controlled by the relay it when connection is made with the trunk-line at the distant terminal, substantially as described.

8. The combination with a telephone trunkline, of a clearing-out signal at one terminal thereof, and a circuit for exciting the signal, nection is removed at the distant terminal of re two relays 71; n controlled by connection with the trunk-line, substantially as described.

the trunk-line at the distant terminal, an in- In Witness whereof I hereunto subscribe my dependent circuit through relayk closed when name this 5th day of August, A. D. 1899.

the same is excited, a shunt for the signal F 5 normally closed by relay 7c and opened when HLNRY MIDDLEBROOK CRANE the same is excited, and a second shunt for lVitnesses: the signal controlled by the relay n, whereby ARTHUR LOOKWOOD, the signal is displayed only when the con- A. P. MORRIS. 

